This invention relates generally to the transfer of semiconductor wafers among various semiconductor processing stations as well as other types of stations, and more particularly to collecting liquid dripping from moving equipment during such transfer.
Semiconductor fabrication requires that a semiconductor wafer be processed in a variety of different manners. A wafer may be coated with photoresist, exposed to an ultraviolet light source to imprint a device pattern on the wafer, developed to remove the exposed photoresist, etched, and so on. Each different type of processing may require that the wafer be moved to a different processing station that is particular to a given type of processing. Therefore, the wafer must usually be transferred among different processing stations in order to fabricate devices on the wafer.
FIG. 1 shows an example system 100 in which wafer transfer is accomplished between a primary unit 102 and a secondary unit 104, as separated conceptually by a dotted line 106 and physically by a wall 110. A chuck 108 having arms 132 moves a container 128 horizontally between the primary unit 102 and the secondary unit 104. The chuck 108 may be such a chuck as manufactured by and available from Robotek International, of Richardson, Tex. The chuck container 128 is more specifically a boat or a cassette. The container 128 moves horizontally as indicated by the arrows 114 and 116. On the side of the primary unit 102, the chuck 108 may at least assist in submersing the container 128, and its contained semiconductor wafers, in an immersion tank 112, for a wet bench process. The chuck 108 may thus move the container 128 to the container position 131.
On the side of the secondary unit 104, a robotic arm 118 is able to move the container 128 vertically into and out of the plane of FIG. 1, as indicated by the in circle 120 and the out circle 122, once the container 128 has been deposited by the chuck 108 in the container position 130. The robotic arm 118 is able to accomplish its movement of the container 128 as a result of its arm 126. The arm 126, as well as the container position 130, is over a stage 124 of the secondary unit 104, as compared to the container position 131, which is over and/or in the tank 112 on the side of the primary unit 102. The robotic arm 118 may be such an arm as manufactured by and available from Kaijo Corp., of Tokyo, Japan. The robotic arm 118 is for moving from a container loading and unloading position, not shown in FIG. 1, to the container position 130, which is a wafer loading and unloading position. By comparison, the container position 131 is a wafer tank immersion position, such that the wafers can be immersed into the tank at this position. The position 131 may alternatively be located in the tank 112 as well.
A problem with the transfer of semiconductor wafers via the system 100 of FIG. 1 is that the caustic chemicals, or other liquid, in which the container 128 is immersed in the tank 112 may drip off chuck 108 when it is moving over the secondary unit 104. The caustic chemicals are those necessary for performing a wet bench operation on the semiconductor wafers held within the container 128. This can cause significant and rapid corrosion of the secondary unit 104, as well as the robotic arm 118 and its arm 128. The chuck 108 and the robotic arm 118 are more generally referred to as moving equipment, insofar as they move, or transfer, the container 128 and its contained semiconductor wafers.
A limited solution to this problem is to clean the chuck 108 before it is moved over the secondary unit 104. For instance, there may be a chuck-cleaning bath in which overflowing deionized water and/or blowing nitrogen clean the residual chemicals from the chuck 108. However, this is disadvantageous a at best. Chuck cleaning prolongs the transfer time from the primary unit 102 to the secondary unit 102, such as by nearly sixty seconds. This lowers the number of wafers that can be processed on a per hour basis, increasing cost to the semiconductor manufacturer. Furthermore, extra facility space is required to house the chuck cleaning bath, which may be expensive at best or not always available at worst. Finally, the cleaning bath cannot completely clean the chuck 108. Therefore, liquid dripping from the chuck 108 is only at best reduced, and thus at best only slows corrosion of the secondary unit 104.
Therefore, there is a need within the art to overcome these disadvantages. Specifically, there is a need to prevent the chuck 108 from corroding the secondary unit 104 and the robotic arm 118 when it is moving over the secondary unit 104. There is a need for complete prevention of such corrosion, and not just a decrease in the rate of corrosion. There is a need to prevent corrosion without slowing down the number of wafers that can be processed on an hourly basis, as well as without requiring extra space in the facility. For these and other reasons, there is a need for the present invention.
The invention relates to stationary and pivotable trays for semiconductor wafer transfer. A first moving equipment, such as a chuck, is movable to move a container for holding one or more semiconductor wafers from a wafer loading and unloading position to a wafer tank immersion position. A second moving equipment, such as a robotic arm, is movable to move the container from the wafer loading and unloading position to a container loading and unloading position. A stationary tray is located under the wafer loading and unloading position to collect liquid dripping from the first moving equipment. A pivotable tray is located to one side of the stationary tray, to collect the liquid dripping from the first moving equipment when this equipment is moving to the wafer loading and unloading position, such that the pivotable tray is lowered. The pivotable tray is raised when the second moving equipment is moving to the wafer loading and unloading position.
The invention provides for advantages over the prior art. The stationary and pivotable trays prevent the liquid dripping from the first moving equipment from corroding the second moving equipment, or other equipment, such as a secondary unit. The trays collect the dripping liquid, such that the first moving equipment does not have to be cleaned in a time-consuming bath, and such that the number of wafers that can be processed on an hourly basis is not decreased. Furthermore, the trays do not use potentially expensive facility space. Other advantages, embodiments, and aspects of the invention will become apparent by reading the detailed description that follows, and by referencing the attached drawings.